2000 articles

Stealth genes and recouping industry's investment

This item -- about work at Texas A&M on overcoming transgene silencing in rice plants -- once again demonstrates our enormous ignorance about the effects of insertion of transgenes. Beneath it we repeat a short recent comment, including references, by Dr Pusztai of relevance to this issue.

An analysis of plant transgene silencing by Dr Phil Dale and a fellow John Innes’ scientist, repeated and enthusiastic reference is made to its generating “valuable new products” and “greater commercial advantage”, as well as to its “...giving industry a valuable opportunity to recoup its investment made in plant biotechnology at an increased rate”. In that context, here's a couple of quotes from a former Texas A&M man:

“The universities are cheering us on, telling us to get closer to industry, encouraging us to consult with big business. The bottom line is to improve the corporate bottom line. It's the way we move up, get strokes.... We can't help but be influenced from time to time by our desire to see certain results happen in the lab.”

“All of these companies have a piece of me. I'm getting checks waved at me from Monsanto and American Cyanamid and Dow, and it's hard to balance the public interest with the private interest. It's a very difficult juggling act, and sometimes I don't know how to juggle it all.” - former Texas A&M University entomologist John Benedict:---

COLLEGE STATION - Texas A&M University biologists are developing genetically modified rice resistant to insects and microbes, which could revolutionize the food and agriculture industries and help alleviate hunger in developing countries.

For many years, spraying insecticides on rice crops has been the best way to protect rice crops from insects. Scientists are now creating new strains of rice plants that would contain insect-killing proteins, so no insecticide would be needed.

"We are interested in killing insects that eat rice plants, like the rice water weevil," says Timothy C. Hall, distinguished professor of biology. "This insect feeds on the leaves and lays its eggs on them. When the eggs hatch, larvae grow and spend about a month chewing the roots."

To protect rice plants from water weevils, Hall and his colleagues insert insect-killing genes in the seeds of rice plants. Ideally, when the plants grow, these genes produce insect-killing proteins in the plant roots, preventing water weevils from eating the roots.

However, Hall and his group discovered that many of the insect-killing genes are not expressed or expressed only in the early stages of the growth of the plants. These genes -- also called transgenes -- are turned off once they are inserted in plants.

"This lack of expression -- also called gene silencing -- is a way for plant cells to protect themselves from invasion," Hall says. "When we put the gene in, it is seen by the plant cells as an invasive event, so there are various ways in which the cells turn off the expression of the foreign gene."

Hall and his colleagues are making new genes that would escape the gene silencing mechanisms.

"We want to create what we call stealth genes, basically genes that can get underneath the radar of the host cell protection," Hall says. "That involves understanding what the actual mechanisms of gene silencing are."

The silencing mechanisms are strategies by which plant cells inactivate and eliminate foreign genes.

Many silencing mechanisms have been encountered by Hall and his colleagues. Their results and those of others have been recently reviewed in the journal Plant Molecular Biology.

An important silencing mechanism consists of methylation, a process by which the introduced gene is modified, so it can be distinguished from the original genes of the cell.

Other silencing mechanisms include the degradation or rearrangement of the transgenes once they enter the cell, prior to their stable integration into the chromosomes.

Hall and his group are also designing fluorescent markers to track down the position of the transgene in the plant cell genome.

"We hope to be able to tell exactly where our genes are inserted and whether it really does make a difference where the transgene is inserted," Hall says.

Hall adds that these studies should be improved when the sequencing of the rice genome is completed in the next few months.

Hall and his colleagues are now developing and testing five different gene constructs that may be able to escape the gene silencing mechanisms, and produce insect-killing proteins. One gene construct is developed in collaboration with the Louisiana Agricultural Experiment Station, while the four others are elaborated in collaboration with Aventis.

"By changing various regions in the transgenes, we hope to be able to make the rice resistant to the water weevil," Hall says. "But we still need to learn a lot about the many ways in which gene silencing is achieved."

Note: This story has been adapted from a news release issued by Texas A&M University for journalists and other members of the public. If you wish to quote from any part of this story, please credit Texas A&M University as the original source. You may also wish to include the following link in any citation: http://www.sciencedaily.com/releases/2000/12/001204071847.htm---

From: Arpad PusztaiTo: This email address is being protected from spambots. You need JavaScript enabled to view it.

Dear Jonathan,

Dr Gregory’s letter would be laughable on account of his ignorance of genetic modification if the consequences of this “well-tried and understood” method were not so serious for us all, including himself.

If he wants to enlighten himself on current research on genetic stability, etc I recommend him to read most of the papers in Plant Molecular Biology, vol. 43, issue 2/3, June 2000. If he is a proper scientist after reading papers, such as “Epigenetic aspects of somaclonal variation in plants”, “Transcriptional gene silencing mutants” and all the papers on gene silencing in this issue, or vol 42 of the same journal, pp 251-269, 2000 entitled: “Transposable element contribution to plant gene and genome evolution” and so on, I am sure he would not write the sort of meaningless propaganda and clap-trap as in his letter!